The great current divide in scientific publishing is between open access articles—that is, those freely available on the internet—and non-open access ones, those for which a reader has to pay on order to gain access to them. Before Jonathan Wren's study appeared (p 1128)1 we knew that open access copies of scientific journal articles published in non-open access (subscription based) journals were a fairly small subset of the overall journal literature.2 Wren studied just which subset it was and found that papers from journals with high impact factors were more likely to have free online copies at other locations around the web than papers from low impact journals.

To show why this matters, and why it's puzzling, let's review what we knew before Wren did his study. We knew that some scientists deposited copies of their published articles in open access repositories, a process called self archiving. We knew that about 80% of subscription based journals allowed their authors to do so.3 Hence, we knew that self archiving was compatible with copyright and with publication in a non-open access journal. We knew that it took an author about 10 minutes to self archive one paper.4 We knew that the open access archives where authors deposited articles were “interoperable,” which means that they conformed to a common standard allowing users to search them all at once, as if they comprised one grand, virtual archive. We knew that there were many …